San Diego developer Doug Manchester said he has agreed to sell 21-month-old La Jolla Pacific to California Federal Savings & Loan Assn. for about $4.5 million. Manchester, the bank's sole shareholder, will make a 50% return on his investment. The sale of the savings bank, which has $42 million in assets, was initiated by Manchester and is expected to be completed within 90 days. It will give CalFed 10 branches in San Diego County, according to spokeswoman Eileen Koontz.